1. Field of the Invention
Embodiments of the invention relate to a hard disk drive (HDD). In particular, embodiments of the invention relate to an HDD adapted to detect free-fall and park a read/write head in a safe position in response to free-fall detection.
This application claims priority to Korean Patent Application Nos. 10-2005-0108525, filed on Nov. 14, 2005 and 10-2006-0029816, filed on Mar. 31, 2006, the collective subject matter of which is hereby incorporated by reference in its entirety.
2. Description of Related Art
A hard disk drive (HDD) is an information storing apparatus commonly used in computers and adapted to read data from and write data to a rotating disk using one or more read/write head(s). In the HDD, an actuator moves the read/write head to a desired position above the disk so that data may be written to or read from an identified location on the disk. During such movements, the read/write head is maintained at a defined “flying height” above the surface of the disk.
However, if the read/write head fails to maintain the defined flying height and collides with the surface of the disk, the surface of the disk may become damaged making data stored at damaged location unreadable. Read/write head collisions with the disk may result from an external impact applied to the HDD. Since HDDs are being more commonly incorporated into portable host devices, the risk of external impacts due to dropping of the host device is increasing. This risk of “disk crash” militates against the incorporation of HDDs into emerging portable devices despite the excellent ratio of price to storage capacity provide by HDDs. However, the obvious commercial advantages provided by HDDs in portable electronic devices has lead to much ongoing research into the design and use of micro HDDs having a size of 1-inch or less.
For example, U.S. Pat. No. RE35,269, the subject matter of which is hereby incorporated by reference, discloses a method for detecting a free-fall state for an HDD (i.e., a condition wherein an HDD is falling under the influence of gravity). This conventional method uses a MEMS (micro-electromechanical system) acceleration sensor to detect the free-fall state and unload a read/write head. The term “unload” is this context refers to an operation wherein a read/write head is moved into a safe position (i.e., a position better immune to the ill-effects of an external impact). However, this conventional approach adds cost and complexity to the HDD design in relation to the incorporation of the MEMS acceleration sensor. Further, the addition of the MEMS acceleration sensor results in an unacceptable increase in the volume of many micro HDD designs intended for use within portable devices, such as mobile phones, PDAs, etc.